Method for the galvano technical manufacture of cylindrical thinwalled screen stencils for the rotary screen printing process

ABSTRACT

A METHOD FOR THE GALVANO TECHNICAL MANUFACTURING OF A SEAMLESS CYLINDRICAL THIN-WALLED STENCIL TO BE USED IN THE ROTARY SCREEN PRINTING PROCESS, SAID METHOD COMPRISING TWO STEPS VIZ DEPOSITING A LAYER OF NICKEL PRIOR TO, OR AFTER THE DEPOSITION OF A LAYER OF ZINC OR COPPER UPON A CYLINDRICAL MATRIX, SO AS TO OBTAIN A TWO-PLY STENCIL.

" United States Patent O 3,713,997 METHOD FOR THE GALVANO TECHNICAL MANUFACTURE OF CYLINDRICAL THIN- WALLED SCREEN STENCILS FOR THE ROTARY SCREEN PRINTING PROCESS Lodewijk Anselrode, Sint Anthonis, Netherlands, assignor to Stork Amsterdam N.V., Amstelveen, Netherlands No Drawing. Filed Feb. 22, 1971, Ser. No. 116,718 Claims priority, application Netherlands, Feb. 20, 1970, 7002467 Int. Cl. C2311 7/02 US. Cl. 204-11 2 Claims ABSTRACT OF THE DISCLOSURE A method for the galvano technical manufacturing of a seamless cylindrical thin-walled stencil to be used in the rotary screen printing process, said method comprising two steps viz depositing a layer of nickel prior to, or after the deposition of a layer of zinc or copper upon a cylindrical matrix, so as to obtain a two-ply stencil.

BACKGROUND OF THE INVENTION The invention relates to a method for manufacturing by means of galvanotechnique cylindrical thin-walled screen stencils for the rotary screen printing process, according to which method a layer of nickel, which is under com-.

pressive stress, is deposited by a galvanic process on a cylindrical metal matrix which-at the location of the perforations in the stencil to be manufactured-is inlaid with a nonconductive material, whereupon the stencil formed is removed from the matrix. Such a method is commonly known and related so far only to a galvano technical manner of manufacturing of stencils, consisting entirely of nickel. In this conventional method nickel is deposited by a galvanic process on a cylindrical metal matrix containing dots of non conductive materials like synthetic resins, glass or glaze in order to form the perforations in the stencil. In order to permit of the formed screen cylinders being removed in an undamaged condition after manufacture it is necessary that at that moment the matrix has an outer diameter, which is slightly smaller than the inner diameter of the screen cylinder formed. This can be achieved by admixing substances to the solution of nickel salts in the galvanic bath, which convert the tensile stress normally present in the coat of nickel into a compressive stress.

An example of such a substance is e.g. saccharine, which for that purpose is used on a large scale. After the formation of the stencil on the matrix it is at first loosened therefrom by mechanical working e.g. with a presser roller and with a considerable pressing force on the whole until the stencil springs loose under the influence of the compressive stress. This operation is further facilitated, when the matrix has been manufactured from a metal with a coefficient of expansion greater than that of nickel. By transferring the matrix with the stencil formed thereon from the nickel bath with a temperature of about 60 C. into a water bath with a temperature of about 20 C., the cylinder shrinks more than the stencil formed theron, so that the latter springs loose sooner.

A drawback of such screen stencils entirely made of nickel is in that they consist of a rather hard and brittle metal and owing thereto crease and tear easily.

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SUMMARY OF THE INVENTION The present invention aims to provide a method by which stencils are obtained, which have not this drawback. Consequently the invention proposes that prior to or after precipitation of the Ni-coat, a layer of a soft metal like Cu or Zn is deposited by a galvanic process on the matrix or on the nickel coat, the arrangement being such that the stencil obtained consists for 25% to of its thickness of nickel. The invention is based on the experience that if only a percentage ranging from 75 to 25 of the thickness of the wall of the stencil formed consists of nickel, in whichpossibly due to the presence of substances like saccharinea compressive stress is present, while the rest of the thickness of the wall consists of another metal which has no or little compressive stress, the compressive stress in the nickel suffices to slide the stencil from the matrix. This is realized after suitable treatment of the matrix with the stencil formed thereon, e.g. by means of the aforementioned presser roller, to enable the stencil to be slid from the matrix without giving rise to injuries, which is due to the difference in diameter between the outer diameter of the matrix and the inner diameter of the stencil formed thereon.

The invention is further based on the surprising discovery that a stencil consisting for only 25 to 75% of nickel and for the rest of a soft metal, which in itself is not suitable for the manufacture of stencils, like electrolytic copper, represents a useful product. Such a stencil has not only sufiicient strength to allow industrial application at a total wall-thickness ranging from 0.06 to 0.3 mm. for the same purposes as for which so far exclusively nickel made stencils could serve, but that in addition thereto these novel stencils present important advantages since they are not so soon damaged owing to the formation of creases and cracks.

The advantages of the method for manufacturing the stencil according to the invention with respect to the conventional methods will be' clarified hereinafter.

DESCRIPTION OF A PREFERRED EMBODIMENT On a matrix a -mesh plainmesh screen cylinder was manufactured in a normal way so that the screen was entirely constructed from nickel precipitated by means of a galvanic process from a so-called Watts bath to which saccharine was added in order to obtain the required compressive stress. The thickness amounted to 80 microns. On the same matrix a new screen cylinder was manufactured by precipitating at first a layer of nickel with a thickness of 40 microns from the aforementioned Watts bath with the same quantity of saccharine. Thereupon the matrix was transferred to an acid copper bath, exclusively containing copper sulphate and sulfuric acid, in which a layer of 40 microns of copper was precipitated on the nickel layer already formed of 40 microns.

From both screen cylinders test strips were cut both in the longitudinal and circumferential direction each strip having a width of 15 cm. The test strips were thereupon bent in an Amsler bending apparatus at a bias of 6 kg. through an angle of the radius of the curvature of the clamps amounting to 1.25 mm. For the two screen cylinders the number of bends was now established at which fracture occurred.

In an apparatus for testing tensile strength strips of 15 mm.s width were thereupon drawn from the two screen cylinders and the force established at which fracture occurred.

Tensile strength in units Circum- Longth ference Normal- 8 8 Nl/Cu 7 6 It appears from these data that the material according to the invention is more resistant to damage caused by bending which in practice is of great importance, while the tensile strength is only slightly reduced.

What I claim is:

1. A method for manufacturing, by means of electro plating, a cylindrical thin-walled two-ply metal screen stencil for the rotary screen printing process, one of the metals being nickel, said method comprising the steps of (a) providing a non-deformable cylindrical metal matrix which is inlaid with a non-conductive material;

(b) depositing a first layer of one of the metals upon the non-deformable cylindrical matrix;

(c) depositing a second layer of the other material upon the first layer, the thickness ratio between the nickel layer and the other layer being between 1:3 and 3: 1;

(d) adding a substance only to the galvanic bath of the nickel precipitation so as to obtain a compression force in the nickel layer; and,

(e) mechanically working the two ply screen stencil on the non-deformable matrix, thereby causing the compressive force to spring the stencil loose.

2. A method as defined in claim 1 wherein the substance added to the galvanic bath is saccharine.

References Cited UNITED STATES PATENTS 2,225,734 12/1940 Beebe 204-11 3,498,891 3/1970 Futterer 204-11 2,166,366 7/1939 Norris 204-11 2,226,381 12/1940 Norris 204-11 2,226,384 12/1940 Norris 204-11 862,145 8/ 1907 Edison 204-9 3,505,177 4/ 1970 Chester et al. 204-9 FOREIGN PATENTS 847,614 9/ 1960 Great Britain 204-11 JOHN H. MACK, Primary Examiner T. TUFARIELLO, Assistant Examiner U.S. Cl. X.R. 204-9 

